Apparent Molar Compressibilities and Volumes of Some 1,1

Feb 23, 2007 - Moreover, the apparent molar isentropic compressibility of all electrolytes has been determined from sound velocity measurements at T ...
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J. Chem. Eng. Data 2007, 52, 699-706

699

Apparent Molar Compressibilities and Volumes of Some 1,1-Electrolytes in N,N-Dimethylacetamide and N,N-Dimethylformamide Anna Płaczek,* Hanna Koziel, and Wacław Grzybkowski Department of Physical Chemistry, Chemical Faculty, Gdan´sk University of Technology, Narutowicza 11/12, 80-952 Gdan´sk, Poland

Densities of solutions of sodium tetraphenylborate, tetraphenylphosphonium bromide, sodium bromide, and sodium perchlorate solutions in N,N-dimethylacetamide and N,N-dimethylformamide have been measured over the concentration range of (0.015 to 0.40) mol‚kg-1 at temperatures between T ) 283.15 K and T ) 333.15 K. From densities, apparent molar volumes and partial molar volumes of the salts at infinite dilution as well as the expansibilities have been evaluated. Moreover, the apparent molar isentropic compressibility of all electrolytes has been determined from sound velocity measurements at T ) 298.15 K. The limiting apparent molar compressibilities have been discussed in terms of possible methods of splitting them into ionic contributions.

Introduction Rational interpretation of thermodynamic properties of solutes requires splitting them into ionic components. Partial molar quantities of individual ions are, due to their additivity, of most interest. Unfortunately, thermodynamics does not give satisfactory clues how to extract ionic contributions. Some extrathermodynamic assumptions need to be accepted, which causes lots of controversies. Hefter and Marcus in their paper discussed in detail all the methods available in the literature for obtaining partial molar volumes of different electrolytes in nonaqueous solvents.1 They recalculated and adjusted some earlier results and proved that reported agreement in values of volumes obtained in different ways was accidental. However, the comparison of all splitting methods led them to the conclusion that the reference electrolyte method based on the observation that V0Φ(Ph4P+) - V0Φ(Ph4B-) ) 2 ( 2 cm3‚mol-1

(1)

and V0Φ(Ph4As+) - V0Φ(Ph4B-) ) 8 ( 2 cm3‚mol-1

(2)

where V0Φ(ion) indicates the partial molar volume of the reference electrolyte ions is the least objectionable split available at the present time. 0 As far as isentropic compressibilities (KS,Φ ) are concerned, there is a little agreement on acceptable methods of dividing them into ionic components. Some approaches have been attempted. Laliberte and Conway used the extrapolation method for obtaining the ionic adiabatic compressibility of halide ions.2 Debashis et al. could not use the same technique since the variation of the limiting apparent molar isentropic compressibilities of tetraalkylammonium bromides relative to the formula weight of cations in DMA was not linear.3 They assumed that the limiting adiabatic compressibility of the bromide ion equals 0. The assumption of Davidson et al., on the other hand, was that the limiting adiabatic compressibility of the tetraphenylborate ion is 0.4 However, their suggestion could be interpreted * Corresponding author. E-mail: [email protected].

Figure 1. Apparent molar volumes VΦ against the square root of molarity c of the Ph4PBr, NaBPh4, NaClO4, and NaBr solutions in DMA and DMF for T ) 298.15 K. Ph4PBr: ], DMA; [, DMF. NaBPh4: 4, DMA; 2, DMF. NaClO4: 0, DMA; 9, DMF. NaBr: O, DMA; b, DMF.

in terms of the equality of some properties of the Ph4P+ and Ph4B- ions. This method was also used by Lankford et al. to 0 into ionic components.5 Singh et al. suggested a divide KS,Φ similar model based on Bu4NBPh4 as a reference electrolyte.6 In this paper, experimental data at T ) 298.15 K for sound velocity and at T ) (283.15, 293.15, 298.15, 303.15, 313.15, 323.15, and 333.15) K for density of sodium tetraphenylborate (NaBPh4, NaTB), tetraphenylphosphonium bromide (Ph4PBr, TPBr), sodium bromide (NaBr), and sodium perchlorate (NaClO4) in N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF) solutions are reported. The apparent molar volume VΦ, adiabatic compressibility κS, and apparent molar 0 adiabatic compressibility KS,Φ are calculated from the measured properties. Standard partial molar thermodynamic quantities of electrolytes are obtained from the extrapolation of their apparent molar values to infinite dilution and then divided into their ionic contributions with the method recommended by Hefter and Marcus.1

10.1021/je060301+ CCC: $37.00 © 2007 American Chemical Society Published on Web 02/23/2007

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Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007

Table 1. Densities G of (C6H5)4PBr, NaB(C6H5)4, NaBr, and NaClO4 Solutions in DMA and DMF at Different Temperatures F/kg‚m-3

ms

F/kg‚m-3

ms

mol‚kg-1 283.15 K 293.15 K 298.15 K 303.15 K 313.15 K 323.15 K 333.15 K mol‚kg-1 283.15 K 293.15 K 298.15 K 303.15 K 313.15 K 323.15 K 333.15 K DMA 0.01406 0.03175 0.04618 0.06104 0.07650

950.021 951.887 954.232 956.145 958.120 960.173

940.804 942.686 945.048 946.975 948.963 951.029

936.193 938.083 940.455 942.389 944.384 946.457

931.578 933.475 935.857 937.799 939.801 941.884

922.331 924.244 926.646 928.605 930.623 932.726

913.054 914.983 917.405 919.382 921.420 923.538

(C6H5)4PBr 903.738 0.09165 905.683 0.1064 908.125 0.1215 910.117 0.1374 912.172 0.1520 914.308

962.188 964.157 966.173 968.299 970.261

953.060 955.046 957.073 959.215 961.195

948.496 950.489 952.528 954.677 956.660

943.929 945.934 947.974 950.132 952.125

934.784 936.799 938.858 941.033 943.041

925.616 927.645 929.724 931.915 933.934

916.412 918.458 920.552 922.764 924.796

DMF 0.01828 0.02382 0.03591 0.04822

958.058 960.516 961.259 962.883 964.538

948.546 951.023 951.772 953.408 955.077

943.780 946.268 947.021 948.665 950.339

939.002 941.503 942.259 943.911 945.592

929.420 931.944 932.707 934.373 936.071

919.790 922.340 923.110 924.792 926.505

910.103 912.676 913.454 915.151 916.880

966.140 968.504 970.959 972.461 974.179

956.692 959.072 961.547 963.064 964.794

951.960 954.353 956.835 958.359 960.095

947.221 949.621 952.115 953.644 955.384

937.712 940.132 942.649 944.188 945.942

928.160 930.600 933.141 934.692 936.461

918.554 921.015 923.585 925.144 926.930

DMA 0.01922 0.03801 0.05466 0.07212 0.09110

950.003 951.332 952.631 953.783 954.993 956.309

940.786 942.143 943.468 944.642 945.876 947.217

936.175 937.547 938.886 940.072 941.317 942.670

931.560 932.946 934.298 935.496 936.752 938.119

922.313 923.728 925.109 926.330 927.613 929.008

913.036 914.482 915.892 917.141 918.452 919.875

NaB(C6H5)4 903.720 0.1083 905.197 0.1260 906.638 0.1446 907.915 0.1611 909.253 0.1786 910.712

957.502 958.738 960.032 961.184 962.402

948.430 949.691 951.009 952.181 953.419

943.894 945.166 946.494 947.677 948.929

939.357 940.642 941.986 943.181 944.443

930.271 931.582 932.953 934.171 935.454

921.166 922.501 923.903 925.144 926.456

912.028 913.392 914.825 916.098 917.435

DMF 0.02586 0.03546 0.05140 0.06859

958.066 959.931 960.623 961.772 963.012

948.546 950.451 951.156 952.327 953.588

943.781 945.702 946.413 947.594 948.866

939.014 940.946 941.661 942.851 944.134

929.430 931.402 932.132 933.344 934.650

919.797 921.807 922.551 923.786 925.118

910.117 912.162 912.920 914.179 915.536

964.225 965.597 967.331 969.175 970.269

954.819 956.215 957.974 959.846 960.955

950.107 951.516 953.29 955.178 956.295

945.386 946.808 948.598 950.507 951.635

935.925 937.372 939.193 941.135 942.282

926.419 927.892 929.750 931.725 932.894

916.863 918.365 920.260 922.276 923.471

DMA 0.03868 0.07570 0.1142 0.1524 0.1896

950.075 953.482 956.712 960.054 963.367 966.587

940.857 944.270 947.505 950.844 954.156 957.368

936.243 939.665 942.900 946.239 949.551 952.763

931.629 935.054 938.292 941.632 944.945 948.155

922.382 925.818 929.062 932.405 935.721 938.935

913.105 916.557 919.805 923.157 926.476 929.697

NaBr 903.788 0.2253 907.255 0.2630 910.522 0.2988 913.876 0.3345 917.208 0.3729 920.430

969.678 972.946 976.045 979.167 982.502

960.462 963.723 966.822 969.937 973.272

955.856 959.116 962.215 965.328 968.663

951.250 954.509 957.608 960.721 964.055

942.030 945.292 948.392 951.506 954.841

932.794 936.062 939.163 942.283 945.617

923.535 926.807 929.920 933.039 936.374

DMF 0.04008 0.06106 0.08045 0.1230 0.1603

958.058 961.622 963.473 965.175 968.894 972.166

948.546 952.116 953.967 955.663 959.378 962.635

943.780 947.353 949.201 950.900 954.612 957.861

939.002 942.582 944.430 946.127 949.837 953.080

929.420 933.009 934.862 936.554 940.257 943.494

919.790 923.390 925.240 926.938 930.633 933.870

910.103 913.710 915.568 917.264 920.960 924.197

0.2020 0.2400 0.2991 0.3558 0.3930

975.812 979.129 984.336 989.324 992.603

966.267 969.568 974.747 979.703 982.961

961.486 964.782 969.946 974.892 978.139

956.699 959.988 965.140 970.076 973.315

947.102 950.382 955.516 960.427 963.652

937.468 940.736 945.860 950.752 953.964

927.787 931.044 936.163 941.044 944.250

DMA 0.03560 0.07279 0.1073 0.1391 0.1787

950.152 953.023 956.021 958.813 961.386 964.607

940.934 943.824 946.841 949.645 952.224 955.462

936.320 939.223 942.250 945.058 947.650 950.892

931.706 934.618 937.656 940.470 943.070 946.319

922.459 925.393 928.452 931.285 933.895 937.167

913.182 916.141 919.221 922.077 924.705 927.996

NaClO4 903.865 0.2122 906.851 0.2471 909.956 0.2817 912.834 0.3171 915.485 0.3508 918.801

967.335 970.186 973.030 975.941 978.735

958.199 961.065 963.911 966.835 969.635

953.635 956.505 959.357 962.288 965.091

949.069 951.946 954.804 957.739 960.546

939.930 942.820 945.692 948.639 951.458

930.776 933.678 936.568 939.529 942.362

921.596 924.524 927.423 930.406 933.248

DMF 0.03096 0.04574 0.07671 0.09316 0.1271

958.066 960.681 961.930 964.547 965.935 968.807

948.546 951.181 952.437 955.067 956.464 959.339

943.781 946.423 947.681 950.315 951.715 954.597

939.026 941.664 942.921 945.560 946.958 949.847

929.444 932.101 933.366 936.018 937.426 940.327

919.808 922.487 923.762 926.430 927.846 930.760

910.117 912.820 914.104 916.790 918.216 921.149

971.196 975.073 978.997 981.621 984.224

961.739 965.626 969.551 972.185 974.784

957.002 960.894 964.822 967.459 970.068

952.254 956.151 960.091 962.730 965.339

942.744 946.654 950.605 953.254 955.867

933.188 937.121 941.077 943.738 946.366

923.580 927.543 931.529 934.185 936.823

Experimental Section Sodium tetraphenylborate, tetraphenylphosphonium bromide, sodium bromide (Fluka, puriss, electrochemical grade), and sodium perchlorate (Aldrich, puriss, analytical grade) were dried under reduced pressure at T ) 308 K. DMA and DMF (Fluka, puriss, absolute, mass fraction H2O < 1‚10-4) were dried with 0.4 nm molecular sieves. Solutions of all salts for density measurements were prepared by weighing diluted stock solutions of the corresponding salt. All preparations and manipulations involving anhydrous materials were performed in dry boxes. The densities of the solutions were measured using an Anton Paar DMA 5000 densimeter with a precision of 1.0·10-3 kg‚m-3 and uncertainties of 5.0·10-3 kg‚m-3 for a single measurement. The instrument was equipped with the Peltier-type thermostating unit, and the temperature was kept constant at T ) (283.15, 293.15, 298.15, 303.15, 313.15, 323.15, and 333.15) K with the precision of 0.001 K according to the manufactureres declaration. The sound velocities were measured using a sound analyzer OPTIME 1.0 from Optel (Poland) with an uncertainty of 0.05

0.06013 0.07767 0.09583 0.1070 0.1196

0.08539 0.1044 0.1283 0.1538 0.1689

0.1552 0.2008 0.2466 0.2771 0.3073

m‚s-1 by measuring the time it takes for a pulse of ultrasound to travel from one transducer to another (pitch-catch) or return to the same transducer (pulse-echo). The cell was thermostated at T ) (298.15 ( 0.005) K and calibrated with double distilled water, and the sound velocity value of 1496.69 m‚s-1 in pure water has been used.7 The value for sound velocity in pure DMF is 1457.14 m‚s-1 while the literature values vary from (1468.0 to 1448.55) m‚s-1.8,9 The velocity of sound in DMA was found to be 1455.37 m‚s-1, while the literature values are in the range from (1456.48 to 1468) m‚s-1.3,10-13

Results and Discussion Apparent Molar Volumes. The apparent molar volume VΦ of a solute is defined as the difference between the volume of the solution and the volume of the pure solvent per mole of solute and is given by the equation: V - n1‚V01 VΦ ) n2

(3)

where V is the volume of the solution; n1 and n2 denote the

Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007 701 Table 2. Apparent Molar Volumes VΦ of (C6H5)4PBr, NaB(C6H5)4, NaBr, and NaClO4 Solutions in DMA and DMF at Different Temperatures 106‚VΦ/m3‚mol-1

ms

106‚VΦ/m3‚mol-1

ms

solvent mol‚kg-1 283.15 K 293.15 K 298.15 K 303.15 K 313.15 K 323.15 K 333.15 K mol‚kg-1 283.15 K 293.15 K 298.15 K 303.15 K 313.15 K 323.15 K 333.15 K DMA

DMF

DMA

DMF

DMA

DMF

DMA

DMF

0.01406 0.03175 0.04618 0.06104 0.07650 0.01828 0.02382 0.03591 0.04822 0.06013

294.61 295.07 295.39 295.61 295.89 291.55 291.73 292.01 292.24 292.46

294.77 295.35 295.71 295.99 296.31 291.85 292.02 292.33 292.55 292.77

294.83 295.42 295.82 296.12 296.47 291.89 292.04 292.34 292.63 292.87

294.95 295.52 295.92 296.25 296.58 291.80 291.99 292.30 292.63 292.87

295.01 295.61 296.01 296.37 296.68 291.75 291.95 292.32 292.61 292.92

295.01 295.64 296.01 296.34 296.72 291.45 291.70 292.11 292.46 292.82

(C6H5)4PBr 294.96 0.09165 295.61 0.1064 296.04 0.1215 296.38 0.1374 296.76 0.1520 291.28 0.07767 291.49 0.09583 291.94 0.1070 292.30 0.1196 292.61

296.14 296.36 296.56 296.72 296.89 292.71 292.94 293.11 293.24

296.56 296.76 297.00 297.17 297.32 293.07 293.30 293.45 293.60

296.72 296.93 297.14 297.33 297.52 293.14 293.42 293.57 293.74

296.86 297.03 297.32 297.50 297.68 293.21 293.48 293.65 293.86

297.03 297.29 297.56 297.75 297.95 293.30 293.57 293.79 294.02

297.06 297.37 297.64 297.87 298.13 293.26 293.54 293.79 294.04

297.00 297.34 297.65 297.88 298.19 293.11 293.34 293.69 293.94

0.01922 0.03801 0.05466 0.07212 0.09110 0.02586 0.03546 0.05140 0.06859 0.08539

283.75 283.85 283.91 283.98 284.04 278.78 278.84 278.95 279.05 279.12

284.13 284.28 284.38 284.46 284.55 279.07 279.20 279.36 279.52 279.68

284.25 284.42 284.55 284.66 284.77 279.37 279.50 279.66 279.82 279.99

284.42 284.62 284.74 284.88 284.98 279.88 280.02 280.13 280.25 280.39

284.66 284.85 285.03 285.16 285.28 280.11 280.25 280.43 280.60 280.77

284.74 284.98 285.13 285.28 285.44 280.38 280.53 280.73 280.90 281.06

NaB(C6H5)4 284.77 0.1083 285.00 0.1260 285.15 0.1446 285.33 0.1611 285.43 0.1786 280.75 0.1044 280.87 0.1283 281.04 0.1538 281.20 0.1689 281.35

284.08 284.15 284.20 284.25 284.30 279.22 279.31 279.41 279.46

284.63 284.69 284.75 284.83 284.90 279.79 279.95 280.09 280.17

284.86 284.94 285.03 285.11 285.17 280.10 280.26 280.41 280.50

285.06 285.14 285.21 285.29 285.38 280.47 280.62 280.73 280.81

285.37 285.46 285.54 285.65 285.77 280.88 281.07 281.20 281.30

285.53 285.66 285.74 285.87 285.99 281.20 281.38 281.57 281.67

285.57 285.72 285.80 285.91 286.06 281.49 281.66 281.84 281.93

0.03868 0.07570 0.1142 0.1524 0.1896 0.04008 0.06106 0.08045 0.1230 0.1603

11.07 11.84 12.48 12.98 13.47 10.88 11.33 11.73 12.45 12.92

10.04 10.85 11.59 12.12 12.69 9.85 10.36 10.89 11.66 12.23

9.34 10.29 11.08 11.64 12.23 9.32 9.92 10.41 11.23 11.87

8.80 9.76 10.58 11.16 11.78 8.66 9.34 9.89 10.77 11.46

7.53 8.58 9.48 10.11 10.75 7.45 8.14 8.84 9.84 10.60

6.05 7.31 8.25 8.94 9.61 6.12 6.99 7.66 8.84 9.62

NaBr 4.53 5.75 6.88 7.58 8.34 4.84 5.65 6.43 7.70 8.54

0.2253 0.2630 0.2988 0.3345 0.3729 0.2020 0.2400 0.2991 0.3558 0.3930

13.87 14.23 14.56 14.81 15.13 13.40 13.80 14.24 14.70 14.96

13.08 13.48 13.82 14.09 14.43 12.78 13.23 13.74 14.25 14.55

12.64 13.06 13.40 13.69 14.03 12.45 12.91 13.47 14.00 14.31

12.19 12.62 12.97 13.27 13.62 12.07 12.57 13.16 13.71 14.04

11.20 11.66 12.03 12.34 12.71 11.29 11.82 12.47 13.09 13.45

10.10 10.57 10.98 11.30 11.70 10.39 11.00 11.69 12.37 12.76

8.85 9.37 9.77 10.14 10.58 9.40 10.08 10.80 11.53 11.95

0.03560 0.07279 0.1073 0.1391 0.1787 0.03096 0.04574 0.07671 0.09316 0.1271

39.80 40.10 40.27 40.42 40.62 36.02 36.14 36.38 36.52 36.74

38.72 39.04 39.27 39.51 39.71 34.74 34.93 35.25 35.40 35.75

38.04 38.43 38.74 38.94 39.19 34.18 34.41 34.77 34.92 35.26

37.48 37.85 38.20 38.40 38.68 34.01 34.22 34.46 34.64 34.92

36.19 36.60 36.99 37.26 37.54 32.66 32.90 33.23 33.40 33.75

34.73 35.24 35.63 35.94 36.27 31.12 31.38 31.82 32.02 32.45

NaClO4 33.13 33.72 34.16 34.47 34.83 29.43 29.76 30.28 30.50 30.98

0.2122 0.2471 0.2817 0.3171 0.3508 0.1552 0.2008 0.2466 0.2771 0.3073

40.74 40.92 41.01 41.16 41.25 36.89 37.12 37.31 37.40 37.53

39.86 40.05 40.18 40.34 40.45 35.91 36.20 36.46 36.56 36.74

39.36 39.57 39.72 39.88 40.01 35.43 35.74 36.03 36.14 36.30

38.86 39.08 39.23 39.41 39.55 35.08 35.39 35.64 35.75 35.93

37.75 38.00 38.18 38.39 38.55 33.94 34.31 34.61 34.74 34.95

36.51 36.81 37.00 37.24 37.42 32.69 33.07 33.48 33.62 33.83

35.13 35.43 35.69 35.94 36.17 31.34 31.71 32.12 32.36 32.61

number of moles of the solvent and solute, respectively; and V01 is the molar volume of the pure solvent. The limiting values of the apparent molar volumes are the primary source of the direct information concerning ion-solvent interaction. In practice, values for the apparent molar volumes can be obtained through the density measurements using the equation VΦ )

M2 F - F 0 F0 mSFF0

(4)

where mS denotes the number of moles of the solute per unit mass of solution (molonity); F and F0 are densities of solution and solvent, respectively; and M2 is the molar mass of the solute. Density data obtained for solutions of the tetraphenylphosphonium bromide, sodium tetraphenylborate, sodium bromide, and sodium perchlorate in DMA and DMF are given in Table 1. The resulting values of VΦ are reported in Table 2. In Figure 1 the apparent molar volumes of NaTB, TPBr, NaBr, and NaClO4 in DMA and DMF are plotted against the square root of molar concentration (c/mol‚dm-3) for T ) 298.15 K. For tetraphenylphosphonium bromide, sodium tetraphenylborate, and sodium perchlorate solutions the plots of VΦ against c1/2 are found to be linear over the concentration as well as temperature range studied. Therefore, Masson’s equation VΦ ) V0Φ + SVc1/2

(5)

where V0Φ and SV are the apparent molar volume of solute at

infinite dilution and the slope, respectively, can be used.14 The coefficients of the Masson’s equation and the respective values of the residual variance obtained for all the solutions and temperatures studied are listed in Table 3. For the sodium bromide solution, the apparent molar volume dependence on the square root of concentration can be described with the Redlich-Rosenfeld-Meyer (RRM)-type equation: VΦ ) V0Φ + AVc1/2 + BVc

(6)

where AV and BV are empirical coefficients. The respective coefficients of the polynomial described by eq 6 and values of the residual variance are given in Table 4. There are data available for the theoretical slope estimation for DMA and DMF, but for T ) 298.15 K only, while our data cover the temperature between T ) 283.15 K and T ) 333.15 K.15 The values of the limiting molar volumes of all salts investigated are a little higher in DMA than the respective values in DMF. The smallest differences were observed for sodium bromide. Those volume differences could be the result of different structure and volume of the two solvents studied. There is also a slight difference in solvation of salts by the two solvents. Ionic Molar Volumes. Limiting apparent molar volumes of NaBPh4, Ph4PBr, NaBr, and NaClO4 were split into ionic components using the reference electrolyte method recommended by Hefter and Marcus.1 The respective values of

702

Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007

Table 3. Coefficients of Equation 5 for Apparent Molar Volume of the Solutions of (C6H5)4PBr, NaB(C6H5)4, and NaClO4 in DMA and DMF at Temperatures between T ) 283.15 K and T ) 333.15 K solvent DMA

DMF

T

106‚V0Φ

106‚SV

106‚σ

106‚V0Φ

106‚SV

106‚σ

K

m3‚mol-1

(m9‚mol-3)1/2

m3‚mol-1

m3‚mol-1

(m9‚mol-3)1/2

m3‚mol-1

283.15 293.15 298.15 303.15 313.15 323.15 333.15

293.58 ( 0.070 293.68 ( 0.069 293.69 ( 0.083 293.76 ( 0.070 293.68 ( 0.079 293.59 ( 0.20 293.54 ( 0.13

0.27 ( 0.010 0.31 ( 0.013 0.32 ( 0.011 0.33 ( 0.009 0.36 ( 0.010 0.38 ( 0.016 0.39 ( 0.016

(C6H5)4PBr 0.026 0.027 0.033 0.027 0.031 0.048 0.044

290.51 ( 0.038 290.76 ( 0.040 290.71 ( 0.042 290.50 ( 0.038 290.31 ( 0.061 289.83 ( 0.087 289.58 ( 0.14

0.254 ( 0.0049 0.265 ( 0.0051 0.283 ( 0.0049 0.314 ( 0.0053 0.347 ( 0.0080 0.40 ( 0.014 0.41 ( 0.018

0.013 0.014 0.013 0.013 0.021 0.031 0.048

283.15 293.15 298.15 303.15 313.15 323.15 333.15

283.47 ( 0.033 283.76 ( 0.035 283.79 ( 0.019 283.98 ( 0.040 284.14 ( 0.055 284.14 ( 0.050 284.13 ( 0.076

0.062 ( 0.0033 0.086 ( 0.0037 0.105 ( 0.0020 0.107 ( 0.0040 0.124 ( 0.0059 0.141 ( 0.0053 0.147 ( 0.0080

NaB(C6H5)4 0.012 0.012 0.006 0.014 0.020 0.019 0.028

278.33 ( 0.016 278.37 ( 0.035 278.66 ( 0.034 279.33 ( 0.047 279.36 ( 0.039 279.57 ( 0.023 279.99 ( 0.031

0.088 ( 0.0014 0.142 ( 0.0038 0.145 ( 0.0039 0.117 ( 0.0050 0.154 ( 0.0044 0.167 ( 0.0027 0.154 ( 0.0035

0.004 0.011 0.012 0.015 0.013 0.007 0.011

283.15 293.15 298.15 303.15 313.15 323.15 333.15

39.12 ( 0.058 37.89 ( 0.039 37.14 ( 0.038 36.51 ( 0.049 35.07 ( 0.054 33.48 ( 0.046 31.73 ( 0.042

0.115 ( 0.0045 0.139 ( 0.0027 0.157 ( 0.0031 0.166 ( 0.0038 0.191 ( 0.0041 0.217 ( 0.0035 0.244 ( 0.0035

NaClO4 0.022 0.014 0.014 0.018 0.020 0.016 0.017

35.30 ( 0.042 33.82 ( 0.074 33.24 ( 0.072 33.13 ( 0.058 31.60 ( 0.060 29.87 ( 0.071 28.01 ( 0.084

0.129 ( 0.0038 0.170 ( 0.0061 0.179 ( 0.0059 0.162 ( 0.0048 0.195 ( 0.0047 0.234 ( 0.0055 0.272 ( 0.0068

0.018 0.031 0.030 0.025 0.024 0.029 0.035

Table 4. Coefficients of Equation 6 for Apparent Molar Volume of the Solutions of NaBr in DMA and DMF at Temperatures between T ) 283.15 K and T ) 333.15 K T

106‚V0Φ

solvent

K

m3‚mol-1

DMA

283.15 293.15 298.15 303.15 313.15 323.15 333.15 283.15 293.15 298.15 303.15 313.15 323.15 333.15

8.59 ( 0.21 7.65 ( 0.13 6.62 ( 0.22 6.00 ( 0.27 4.43 ( 0.25 2.57 ( 0.18 0.78 ( 0.38 8.51 ( 0.20 7.06 ( 0.23 6.37 ( 0.17 5.38 ( 0.17 3.63 ( 0.29 1.87 ( 0.21 0.24 ( 0.38

DMF

106‚AV

109‚BV

106‚σ

(m9‚mol-3)-1/2 (m3‚mol-1)2 m3‚mol-1 0.36 ( 0.039 0.41 ( 0.052 0.47 ( 0.040 0.49 ( 0.044 0.55 ( 0.045 0.63 ( 0.031 0.68 ( 0.067 0.40 ( 0.034 0.48 ( 0.041 0.51 ( 0.028 0.58 ( 0.033 0.67 ( 0.050 0.76 ( 0.035 0.81 ( 0.069

-1.7 ( 1.4 -2.6 ( 1.9 -4.5 ( 1.5 -4.6 ( 1.8 -5.8 ( 1.7 -7.8 ( 1.2 -8.2 ( 2.6 -3.8 ( 1.3 -4.9 ( 1.5 -5.3 ( 1.1 -6.8 ( 1.1 -8.6 ( 1.9 -10.2 ( 1.4 -10.8 ( 2.6

0.027 0.038 0.028 0.034 0.032 0.022 0.049 0.027 0.031 0.023 0.023 0.040 0.028 0.053

Table 5. Values of the Limiting Partial Molar Volumes of the Tetraphenylphosphate, Tetraphenylborate, Sodium, Bromide, and Perchlorate Ions in DMA and DMF at Temperatures between T ) 283.15 K and T ) 333.15 K 106‚V0Φ/m3‚mol-1

T K

solvent

283.15

DMA DMF DMA DMF DMA DMF DMA DMF DMA DMF DMA DMF DMA DMF

293.15 298.15 303.15 313. 15 323.15 333.15

(C6H5)4

P+

285.23 281.17 285.90 282.04 286.43 282.50 286.87 283.23 287.70 284.02 288.58 284.77 289.45 285.66

(C6H5)4B-

Na+

Br-

ClO4-

283.23 279.17 283.90 280.04 284.43 280.50 284.87 281.23 285.70 282.02 286.58 282.77 287.45 283.66

0.24 -0.83 -0.14 -1.67 -0.64 -1.84 -0.89 -1.89 -1.56 -2.66 -2.44 -3.19 -3.32 -3.67

8.35 9.34 7.79 8.73 7.26 8.21 6.89 7.27 5.99 6.29 5.01 5.06 4.10 3.91

38.88 36.14 38.03 35.49 37.78 35.08 37.40 35.03 36.63 34.26 35.92 33.07 35.05 31.69

V0Φ(ion) in DMA and DMF within the whole temperature range are listed in Table 5. Figure 2 shows the plots of the 0 0 difference VΦ,T (ion) - VΦ,283.15 (ion) against temperature for both solvents. As is seen, for the tetraphenylphosphonium and

tetraphenylborate ions, the limiting apparent molar volume increases with temperature. This effect is caused by weak solvation as well as an increase in the intrinsic volumes of the ions. As for the sodium, bromide, and perchlorate ions, a decrease of partial molar volumes with temperature is observed. However, the influence of temperature appears to be higher for anions than the sodium cation, which considering better solvation for cations, seems to be incorrect. The reason for this is probably connected with the assumption V0Φ(Ph4P+) V0Φ(Ph4B-) ) 2 ( 2 cm3 ‚mol-1, which is used through the whole temperature range. Data analysis suggests, that in order 0 0 (ion) - VΦ,283.15 (ion) gradation, a gradual to obtain correct VΦ,T decrease in the values of the difference of volumes of tetraphenylphosphonium and tetraphenylborate ions with increasing temperature should be used. The changes of ionic volumes with temperature should be evaluated by using extrapolation techniques, which do not impose defined relations hips between cation and anion volumes. Volume Expansibilities. The limiting values of the apparent molar volumes of sodium bromide and sodium perchlorate in both solvents depend on temperature, while for tetraphenylphosphonium bromide and sodium tetraphenylborate the volume change with increasing temperature is very slight and smaller than 1 cm3. The volume expansibilities for the limiting values of the apparent molar volumes are defined using the equation RV0 )

( )

0 1 ∂VΦ ‚ V0Φ ∂T

P

(7)

and calculated for T ) 298.15 K. The derivative in eq 7 was calculated on the basis of the polynomial (eq 8) describing the limiting values of the apparent molar volumes dependence on temperature: V0Φ ) AT + BT‚(T/K - 298.15) + CT‚(T/K - 298.15)2 (8)

Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007 703

0 Figure 2. Plots of the difference V0Φ - VΦ,283.15 for TP+, TB-, Na+, Br-, and ClO4- ions in DMA and DMF against temperature T. TP+ ) TB-: ], DMA; + [, DMF. Na : 4, DMA; 2, DMF. ClO4-: 0, DMA; 9, DMF. Br -: O, DMA; b, DMF.

Figure 3. Plots of the adiabatic compressibilties κS of Ph4PBr, NaBPh4, NaClO4, and NaBr solutions in DMA and DMF against the square root of molarity c for T ) 298.15 K. Ph4PBr: ], DMA; [, DMF. NaBPh4: 4, DMA; 2, DMF. NaClO4: 0, DMA; 9, DMF. NaBr: O, DMA; b, DMF.

The values of volume expansibilities and the coefficients of eq 8 are listed in Table 6 along with the respective values of residual variance. As is seen, the values of the expansibility for sodium bromide and sodium perchlorate are in good agreement with each other in DMA and in DMF. The values of the expansibilities of tetraphenylphosphonium bromide and sodium tetraphenylborate are very small in the two solvents investigated. Thus we can assume that the limiting apparent molar volumes of Ph4PBr and NaBPh4 do not depend on temperature. However, in this case it does not mean that the limiting apparent molar volumes of ions do not change with temperature. For large tetraphenyl ions like the tetraphenylphosphonium cation or tetraphenylborate anion, the limiting apparent molar volume increases with temperature, whereas V0Φ of the small Na+ and Br- ions decreases with rising temperature. From this observation, we can assume that the two effects cancel each other out, which causes such small values for the volume expansibilities.

Apparent Molar Isentropic Compressibilities. The adiabatic compressibility is defined by the thermodynamic relation 1 ∂V κS ) - ‚ V ∂P

( )

S

(9)

where V is volume, P is pressure, and S is entropy. It is related to density F and sound velocity u by the Laplace equation: κS )

1 u2F

(10)

Apparent molar isentropic compressibility is defined by the equation KS,Φ )

V‚κS - n1‚V01‚κ0S n2

(11)

where V is the volume of the solution; n1 and n2 denote the

704

Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007

Table 6. Parameters of Equation V0Φ ) AT + BT‚(T/K - 298.15) + CT‚(T/K - 298.15)2 and Volume Expansibility r0V for (C6H5)4PBr, NaB(C6H5)4, NaBr, and NaClO4 Solutions in DMA and DMFa

solvent

a

AT

BT

103CT

σ

103R0V

cm3‚mol-1

cm3‚mol-1

cm3‚mol-1

cm3‚mol-1

K-1

0.033 0.143

0.0114 ( 0.0116 -0.0272 ( 0.0503

0.078 0.249

0.0714 ( 0.0280 0.13 ( 0.095

-0.66 ( 0.59 -0.54 ( 0.61

0.166 0.174

-22 ( 2.2 -25 ( 2.3

-0.47 ( 0.25 -0.53 ( 1.16

0.069 0.331

-3.7 ( 0.22 -3.8 ( 1.1

(C6H5)4PBr 0.0034 ( 0.0035 -0.2 ( 0.15 -0.0079 ( 0.015 -8.1 ( 5.2

DMA DMF

293.69 ( 0.083 290.71 ( 0.042

DMA DMF

283.79 ( 0.019 278.66 ( 0.034

DMA DMF

6.62 ( 0.22 6.37 ( 0.17

-0.14 ( 0.020 -0.16 ( 0.018

DMA DMF

37.14 ( 0.038 33.24 ( 0.072

-0.14 ( 0.011 -0.13 ( 0.039

0.020 ( 0.0084 0.035 ( 0.026

NaB(C6H5)4 -0.27 ( 0.28 0.11 ( 0.88 NaBr

NaClO4

0 Coefficient AT is equal to VΦ,298.15 .

Table 7. Sound Velocities u, Adiabatic Compressibilities KS, and Apparent Molar Compressibilities KS,Φ of (C6H5)4PBr, NaB(C6H5)4, NaBr, and NaClO4 Solutions in DMA and DMF at the Temperature 298.15 K ms

u

1010‚κS

1014‚KS,Φ

ms

u

1010‚κS

1014‚KS,Φ

mol‚kg-1

m‚s-1

m2‚N-1

m5‚mol-1‚N-1

mol‚kg-1

m‚s-1

m2‚N-1

m5‚mol-1‚N-1

DMA 0.008695 0.01672 0.02591 0.03470 0.04309 0.05227 0.06073 0.06911 0.07773 0.08651

1455.37 1456.48 1457.48 1458.65 1459.78 1460.86 1462.09 1463.16 1464.32 1465.46 1466.70

5.043 5.029 5.016 5.002 4.988 4.974 4.960 4.946 4.933 4.919 4.904

1457.13 1459.04 1459.65 1460.99 1462.41 1463.80 1465.92 1468.17 1469.60 1471.24

4.990 4.964 4.956 4.938 4.920 4.903 4.876 4.849 4.831 4.812

-5.47 -6.05 -6.46 -7.08 -7.35 -7.92 -8.27 -8.60 -8.82

DMA 0.01559 0.02993 0.04447 0.06051 0.07546 0.09038 0.1056 0.1206 0.1355 0.1515

1455.37 1456.71 1457.91 1459.12 1460.47 1461.71 1462.96 1464.23 1465.49 1466.73 1468.04

5.043 5.028 5.014 5.000 4.985 4.971 4.957 4.942 4.928 4.914 4.900

DMF 0.01418 0.02142 0.02852 0.04246 0.05507 0.07020 0.08415 0.09795 0.12015

1457.13 1457.88 1458.39 1458.90 1460.02 1461.15 1462.55 1464.03 1465.56 1467.98

4.990 4.980 4.973 4.967 4.954 4.942 4.926 4.911 4.896 4.871

5.59 5.34 5.20 4.87 4.58 4.33 4.03 3.78 3.54

DMA 0.05475 0.1073 0.1551 0.2092 0.2592 0.3081 0.3593 0.4124 0.4591 0.5024

1455.37 1457.93 1460.10 1461.96 1463.87 1465.61 1467.09 1468.88 1470.68 1472.12 1473.56

5.043 4.999 4.960 4.926 4.889 4.856 4.824 4.791 4.756 4.727 4.700

DMF 0.04008 0.06106 0.08045 0.1229 0.1603 0.2020 0.2400 0.2991 0.3558 0.3930

1457.13 1459.05 1459.96 1460.77 1462.45 1463.87 1465.66 1467.09 1469.24 1471.04 1472.48

4.990 4.958 4.943 4.928 4.898 4.872 4.842 4.816 4.776 4.740 4.715

-7.93 -7.74 -7.59 -7.32 -7.13 -7.04 -6.90 -6.72 -6.51 -6.44

DMA 0.04049 0.08250 0.1276 0.1682 0.2089 0.2511 0.2898 0.3335 0.3749 0.4170

1455.37 1457.63 1459.76 1461.96 1463.93 1465.82 1467.81 1469.70 1471.76 1473.83 1475.84

5.043 5.009 4.976 4.942 4.911 4.882 4.851 4.822 4.791 4.761 4.731

DMF 0.01435 0.03096 0.04574 0.07671 0.12708 0.15522 0.20077 0.24660 0.27706 0.30730

1457.13 1457.94 1458.84 1459.61 1461.23 1463.82 1465.30 1467.55 1469.96 1471.40 1472.84

4.990 4.978 4.965 4.953 4.928 4.889 4.867 4.832 4.797 4.774 4.752

-7.18 -7.02 -6.91 -6.78 -6.61 -6.56 -6.42 -6.34 -6.26 -6.18

KS,Φ )

M2‚κ0S κ0Sd - κSF0 F0 mSFF0

(C6H5)4PBr -2.01 -1.98 -2.00 -1.99 -1.97 -2.00 -1.93 -1.96 -1.92 -1.95

DMF 0.01828 0.02382 0.03591 0.04822 0.06013 0.07767 0.09583 0.1069 0.1196 NaB(C6H5)4

3.94 4.03 4.10 4.13 4.19 4.22 4.26 4.30 4.34 4.39 NaBr -7.96 -7.56 -7.32 -7.07 -6.88 -6.68 -6.55 -6.42 -6.29 -6.20 NaClO4 -6.72 -6.53 -6.35 -6.23 -6.09 -5.98 -5.90 -5.80 -5.73 -5.65

number of moles of the solvent and solute, respectively; V01 is the molar volume of the pure solvent; κS and κ0S are the adiabatic compressibilities of solution and solvent. The apparent molar isentropic compressibilities for all salts investigated were calculated on the basis of the equation

(12)

where M2 is the molecular mass of the salt; mS denotes a number

Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007 705

Figure 4. Plots of the apparent molar adiabatic compressibilties KS,Φ of Ph4PBr, NaBPh4, NaClO4, and NaBr solutions in DMA and DMF against the square root of molarity c for T ) 298.15 K. Ph4PBr: ], DMA; [, DMF. NaBPh4: 4, DMA; 2, DMF. NaClO4: 0, DMA; 9, DMF. NaBr: O, DMA; b, DMF. Table 8. Coefficients of Equation KS ) K0S + A1c1/2 + A2c for Adiabatic Compressibilities of the Solutions of (C6H5)4PBr, NaB(C6H5)4, NaClO4, and NaBr in DMA and DMF at the Temperature 298.15 K, Where K0S ) 5.043‚10-10 m2‚N-1 for DMA and K0S ) 4.990‚10-10 m2‚N-1 for DMF (C6H5)4PBr

NaB(C6H5)4

1014‚A1/(m7‚N-2‚mol-1)1/2 1014‚A2/m5‚N-1‚mol-1 1010‚σ/m2‚N-1

-0.4 ( 0.7 -16.84 ( 0.085 0.0001

DMA -3 ( 1.5 -9.7 ( 0.14 0.0003

1014‚A1/(m7‚N-2‚mol-1)1/2 1014‚A2/m5‚N-1‚mol-1 1014‚σ/m2‚N-1

4.7 ( 0.72 -15.93 ( 0.078 0.0001

DMF 19 ( 4.9 -12.1 ( 0.55 0.0010

NaClO4

NaBr

-15 ( 3.1 -7.0 ( 0.19 0.0011

-24 ( 5.0 -5.9 ( 0.30 0.0021

-7 ( 3.5 -7.6 ( 0.23 0.0011

-15 ( 4.9 -6.4 ( 0.29 0.0019

Table 9. Coefficients of Equation 14 for Apparent Molar Adiabatic Compressibilities of the Solutions of (C6H5)4PBr, NaB(C6H5)4, NaClO4, and NaBr in DMA and DMF at the Temperature 298.15 K (C6H5)4PBr

NaB(C6H5)4

NaClO4

NaBr

0 1014‚KS,Φ /m5‚mol -1‚N-1 1016‚SK/(m13‚mol-3‚N-2)1/2 1014‚σ/m5‚mol-1‚N-1

-2.05 ( 0.025 1.2 ( 0.83 0.021

DMA 3.74 ( 0.025 5.3 ( 0.27 0.009

-7.20 ( 0.011 7.8 ( 0.21 0.010

-8.74 ( 0.042 11.7 ( 0.57 0.034

0 1014‚KS,Φ /m5‚mol-1‚N-1 16 10 ‚SK/(m13‚mol-3‚N-2)1/2 1014‚σ/m5‚mol-1‚N-1

-0.36 ( 0.031 -4.9 ( 0.42 0.011

DMF 6.7 ( 0.12 -30 ( 1.8 0.041

-7.40 ( 0.048 7.0 ( 0.42 0.023

-8.55 ( 0.098 10.9 ( 0.70 0.040

of moles of the solute per kilogram of solution (molonity); and F and F0 are the densities of solution and solvent, respectively. The symbols κS and κ0S are explained above. Values of sound velocities, adiabatic compressibilities, and apparent molar isentropic compressibilities along with the corresponding molonity of each solution are listed in Table 7. It has been found that for all of the solutions investigated the plots of adiabatic compressibility κS against concentration are not linear and the best description is obtained using the equation: κS ) κ0S + A1c1/2 + A2c

(13)

where κ0S in Pa-1 is the adiabatic compressibility of the pure solvent at T ) 298.15 K. Coefficients A1 and A2 as well as the respective values of residual deviations are given in Table 8. The concentration dependencies of the adiabatic compressibility

coefficients for solutions of NaTB, TPBr, NaClO4, and NaBr in DMA and DMF at 298.15 K are presented in Figure 3. In both solvents investigated the tendency of the changes observed is similar. Among the salts studied the highest impact on solution compressibility is from tetraphenylphosphonium bromide and sodium tetraphenylborate. Because of the complex structure of TP+ and TB- ions consisting of four stiff phenyl rings, the influence of the corresponding salts on solution compressibilities is quite significant, even though their interactions with the solvent are weak. In Figure 4 the values of the apparent molar compressibilities of Ph4PBr, NaBPh4, NaClO4, and NaBr are presented as a function of the square root of concentration. As can be seen, all the plots are linear indicating, that the equation 0 KS,Φ ) KS,Φ + SKc1/2

(14)

706

Journal of Chemical and Engineering Data, Vol. 52, No. 3, 2007

0 where KS,Φ represents the limiting apparent molar adiabatic compressibility and SK is the experimental slope, may be used for extrapolation. Equation 14, which has the form analogous to the Masson’s equation, was first introduced and applied by Gucker.16 The coefficients of eq 14, their uncertainties as well as the respective values of the residual deviations σ are collected in Table 9. All salts investigated have little influence on solvent compressibility. Positive values of apparent molar compressibility of NaBPh4 indicate that its presence in solution breaks the solvent structure. This effect is attributed to the TB- ion since it has been established from NMR17 as well as DRS18 measurements that Na+ is a structure-making ion. This statement is also confirmed by negative values of limiting apparent molar volumes of the sodium ion in DMA and DMF. In the case of TPBr, the values of the apparent molar adiabatic compressibilities are negative, which suggests that the tetraphenylphosphonium ion is better solvated in comparison to the tetraphenylborate anion. Therefore it is evident that assuming equality of compressibilities of the reference electrolyte ions in order to evaluate ionic contributions is an oversimplification. It also seems to be obvious that in the case of other reference electrolytes like Bu4NBPh4 this assumption is particularly inadequate.

Conclusions 0 0 Assuming the equality of KS,Φ (TP+) and KS,Φ (TB-), the 0 -14 5. negative values of KS,Φ(Br ) (-10.22·10 m mol-1.N-1 for DMA and -7.81·10-14 m5.mol-1.N-1 for DMF) and 0 KS,Φ (ClO4-) (-5.73·10-14 m5.mol-1.N-1 for DMA and -6.66· 10-14 m5.mol-1.N-1 for DMF) were obtained. These results suggest that the latter two anions decrease the compressibility of the solvent much stronger than does the sodium cation. This is in contradiction with the results of other studies confirming better solvation of cations in both solvents investigated. However, the reference electrolyte method is still the best way for obtaining ionic volumes of many electrolytes. Marcus and Hefter estimated that the intrinsic volume of the TP+ and TBions reaches 95 % of the whole ion volume.1 This means that the differences in solvation of the TP+ and TB- ions have the slightest impact on values of ionic volumes. On the other hand, the intrinsic compressibility of the ions is very small, and that is why the reference electrolyte method is not suitable for dividing the limiting apparent molar adiabatic compressibilities into ionic contributions.

Literature Cited (1) Hefter, G.; Marcus Y. A. Critical review of methods for obtaining ionic volumes in solution. J. Solution Chem. 1997, 26, 249-266. (2) Laliberte, L. H.; Conway, B. E. Solute and solvent structure effects in volumes and compressibilities of organic ions in solution. J. Phys. Chem. 1970, 74 (23), 4116-4125.

(3) Debashis, D.; Bijan, D.; Hazra, D. K. Ultrasonic velocities and isentropic compressibilities of some symmetrical tetraalkylammonium salts in N,N-dimethylacetamide at 298.15 K. J. Mol. Liq. 2004, 111, 15-18. (4) Davidson, I.; Perron, G.; Desnoyers, J. E. Isentropic compressibilities of electrolytes in acetonitrile at 25 °C. Can. J. Chem. 1981, 59, 22122217. (5) Lankford, J. I.; Holladay, W. T.; Criss, C. M. Isentropic compressibilities of univalent electrolytes in methanol at 25 °C. J. Solution Chem. 1984, 13 (10), 699-720. (6) Singh, J.; Kaur, T.; Ali, V.; Gill, D. S. Ultrasonic velocities and isentropic compressibilities of some tetraalkylammonium and copper(I) salts in acetonitrile and benzonitrile. J. Chem. Soc. Faraday Trans. 1994, 90 (4), 579-582. (7) Del Gross, V. A.; Mader, C. W. Speed of sound in pure water. J. Acoust. Soc. Am. 1972, 52, 144-1446. (8) Ali, A.; Nain, A. K.; Kamil, M. Physico-chemical studies of nonaqueous binary liquid mixtures at various temperatures. Thermochim. Acta 1996, 274, 209-221. (9) Gill, D. S.; Anand, H.; Puri, J. K. Isentropic compressibilities of some copper(I), sodium(I) and tetraalkylammonium salts evaluated from ultrasonic velocity measurements in acetonitrile + N,N-dimethylformamide mixtures at 298.15 K. J. Mol. Liq. 2003, 108 (1-3), 265282. (10) Aminabhavi, T. M.; Gopalakrishna, B. Density, viscosity, refractive index, and speed of sound in aqueous mixtures of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, acetonitrile, ethylene glycol, diethylene glycol, 1,4-dioxane, tetrahydrofuran, 2-methoxyethanol, and 2-ethoxyethanol at 298.15 K. J. Chem. Eng. Data 1995, 40, 856-861. (11) Aralaguppi, M. I.; Jadar, C. V.; Ortego, J. D.; Mehrotra, S. C. Density, refractive index, and speed of sound in binary mixtures of 2-ethoxyethanol with dimethyl sulfoxide, N,N-dimethylformamide, and N,Ndimethylacetamide at different temperatures J. Chem. Eng. Data 1997, 42, 301-303. (12) Ali, A.; Nain, A. K. Ultrasonic study of molecular interactions in N,Ndimethylacetamide + ethanol binary mixtures at various temperatures. Acoust. Lett. 1996, 19, 181. (13) Aminabhavi, T. M.; Patil, V. B. Density, viscosity, refractive index, and speed of sound in binary mixtures of ethenylbenzene with N,Ndimethylacetamide, tetrahydrofuran, N,N-dimethylformamide, 1,4dioxane, dimethyl sulfoxide, chloroform, bromoform, and 1-chloronaphthalene in the temperature interval (298.15-308.15) K. J. Chem. Eng. Data 1998, 43, 497-503. (14) Masson, D. O. Solute molecular volumes in relation to solvation and ionization. Philos. Mag. 1929, 8, 218-235. (15) Marcus, Y. The Properties of SolVents; John Wiley & Sons: London, 1998. (16) Gucker, F. T. The compressibility of solutions. I. The apparent molal compressibility of strong electrolytes. J. Am. Soc. Chem. 1933, 55 (7), 2709-2718. (17) Rao, Ch. P.; Balaram, P.; Rao, N. R. 13C nuclear magnetic resonance studies of the binding of alkali and alkaline earth metal salts to amides J. Chem. Soc. Faraday Trans. 1 1980, 76, 1008-1013 (18) Wurm, B.; Munsterer, M.; Richardi, J.; Buchner, R.; Barthel, J. Ion association and solvation of perchlorate salts in N,N-dimethylformamide and N,N-dimethylacetamide. A dielectric relaxation study. J. Mol. Liq. 2005, 119, 97-106.

Received for review July 4, 2006. Accepted January 20, 2007.

JE060301+